Tim Brannan of The Other Side blog wrote a recent post on the history of Orcus, along with a conversion to Unisystem. His post is well worth a read.
He also posted the above illustration, which first appears in The Dragon Magazine, Issue 42, October 1980. He was not sure who the artist was, nor when it was published. The illustration is by an artist by the name of Todd Lockwood. This is perhaps my favorite Orcus illustration, showing Orcus sitting lazily on his throne: I can't be sure whether he is snoring or drooling.